photos people not showing

Both, iCloud Photos and a system upgrade can be causing conflicts between the recognized faces by the previous system version or between the face recognition on the synced devices.In that case Photos may be waiting for a confirmation of the detected faces. Have you been using the command "Confirm additional faces"

for the faces album, where you are missing faces? try this, before you add missing faces manually again.

And, after a system upgrade we should give Photos a lot of time to finish the face detection. After the upgrade to Ventura it took three weeks, until most of the faces came back. Photos has a lot of scanning and analyzing to do.

What has changed on your Mac? Did you just upgrade the Mac to macOS 14 Mojave? Or when did the problem first occur?